Tag Archives: warm nights

Avoiding drought

October raw anomaly data (orange)

October 2017 was moist: all moisture indicators had dropped sharply down the graphs, retreating from the aridity of August and September. Daily maximum temperature anomaly (x-axis in all graphs) fell towards normal, while that of the subsoil (lower right graph) remained low. Daily minimum temperature anomaly (lower left graph) jumped from extremely low to extremely high.

Fully smoothed data (red)

The latest fully-smoothed data point is that for April 2017.
At that time, the climate was warm and almost static. There was a pause in a drift towards aridity.

Note:

Fully smoothed data – Gaussian smoothing with half-width 6 months – are plotted in red, partly smoothed data uncoloured, and raw data for the last data point in orange. January data points are marked by squares.Blue diamonds and the dashed blue rectangle show the extreme values in the fully smoothed data record since September 1999.

Normal values are based on averages for the decade from March 1999.* They appear on these graphs as a turquoise (turquoise) circle at the origin (0,0). A range of anomalies called “normal” is shown by a dashed rectangle in aqua (aqua). For values in degrees, the assigned normal range is +/-0.7°; for cloudiness, +/-7%; for monthly rainfall, +/-14 mm.

* Normal values for rainfall are based on averages for the 125 years beginning 1883.

March 2017 had 17 rain days. In 134 years, this was beaten only by June 1950, which had 18. [See Note below: “Manilla rain day statistics”]

Weeping Myall

After the record high temperatures of February, day and night temperatures in March were normal, without extremes. On a weekly basis, the first half of the month was cooler than the second half. The subsoil temperature followed the weekly air temperature down, to be a degree below normal by the 20th.
The second week had mainly clear skies and low dew points, Then the skies became persistently cloudy and dew points were high. A number of afternoons had oppressive humidity, with minimum values over 70%.
Of the 17 rain days, only three were early in the month, and they had little rain. The highest daily reading of 15.0 mm came on the 22nd.

Comparing March months

March had been sunny and very warm in both 2016 and 2015. This March was like that of 2014 and 2013, but with even more moisture. The mean average temperature was normal but, due to the cloudiness (58% cloudy mornings), the mean daily maximum, 29.1° was low and the mean daily minimum, 16.4°, was high, yielding the record narrow daily temperature range for March of 12.7°. The mean early morning dew point, 13.7°, was the highest March value in a decade, and the mean afternoon humidity minimum, at 53%, was far above the usual value of 30%.
The total rainfall of 113.2 mm was at the 90th percentile, far above the March average of 54 mm. The previous month, February, had only 4.1 mm, at the 4th percentile for that month. Taken together the two-month total of 117.3 mm was well above normal, at the 63rd percentile.

[Note: Manilla rain day statistics

This near-record number of rain days in a month (17) was more remarkable for being in March, a month with with only 4.8 rain days on average. Most months of the year have about six rain days on average, but the autumn months of March, April, and May have an average of 4.6 rain days per month. The averages are posted here.]

Data. In 2016, a Bureau of Meteorology automatic rain gauge (formerly used for flood prediction) was set up in the museum yard as the official Manilla rain gauge. From 23 May 2016, its daily readings were published as if from Manilla Post Office, Station 55031. The gauge ceased transmitting five months later, on 7 October 2016. This month, after repair, it came into operation again. From 17 March 2017, daily readings are now published as Manilla Museum, Station 55312.

In these reports,the rainfall data is from Station 55031 or Station 55312 when available. Otherwise, rainfall data is from 3 Monash Street, Manilla. All other data, including subsoil at 750 mm, are also from there.

The second cloudiest month of this century brought the warmest July night.
There were two very warm spells in the trace of weekly average temperature. Both were due mainly to warm nights. The second spell, coming in the third week, reached nearly six degrees above normal. On the morning of Saturday the 23rd, the minimum reading on the screen thermometer, 14.4°, was the highest July minimum in the record from 1999.
Up to the 25th, the weather was changeable, with some days overcast and rainy, and others fine and sunny. A very warm sunny day on the 17th, following a frost, had the unusually wide daily temperature range of 21.9°. From the 25th, the weather settled to what is normal for July. In the whole month, there were sixteen frosts, which is normal.
The highest rainfall reading was only 11.4 mm. Ten days had rainfall recorded, but three of these had 0.2 mm, on days when rain was not seen.

Comparing July months

The mean daily maximum temperature (16.9°) was normal. The mean daily minimum temperature (4.0°) was two degrees above normal, making the average temperature (10.5°) one degree above normal. Similarly, the subsoil temperature (14.7°) was one degree above normal.
The daily temperature range, normally 15.0°, was 12.9°, not quite as narrow as in 2010 (12.3°). The early morning dew point was normal. At 2.2°, it was so close the the daily minimum temperature (4.0°) that fogs were to be expected.
The month was extraordinarily cloudy. Cloud cover is assessed by the number of octas (eighths) of the sky seen to be covered by cloud at 9 am. I compare cloudiness of months by the percentage of “cloudy mornings”: those when I see more than four octas of cloud. This month, with 21 cloudy mornings, had 68%. July normally has only 35%. The only month in this century with a higher value was June 2013, with 73%.
The monthly rainfall total of 32.4 mm is below the average (41 mm), in the 47th percentile. The greatest rainfall “shortage” is now in the 48-month total (2221 mm) which is in the 14th percentile. Both Greenhatch Creek and Rushes Creek are just flowing.

Data. Rainfall figures for this month are from the automatic rain gauge at Manilla, published on the internet by the Bureau of Meteorology as Station 55031. All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

Two very warm nights

On two mornings this month, the 21st and 23rd, the minimum temperature in my thermometer screen was higher than it has ever been in July. That is, in the 17-year record that I began in March 1999.
These minimum readings were 14.3° and 14.4°. The highest July minimum had been 13.5° (31/07/2010), and only five readings had ever been above 12°. Such readings are more than ten degrees higher than normal in July.
In fact, one of the nights was much warmer than the minimum temperature indicates.

Minima not always at night

High minimum temperature readings are the usual evidence of warm nights. Unfortunately, they are not the same thing. Especially in the case of very high readings, they can be misleading.
The catch is that we expect daily maximum temperature to occur in daytime, when the sun is in the sky, and daily minimum temperature to occur at night, when it is not. In Manilla’s very sunny climate, the maximum is usually about fifteen degrees higher than the minimum. We can expect the maximum about 3 pm, and the minimum about 6 am.
When a thermometer is read at 9 am (as they are), the maximum reading recorded on it is usually that of the afternoon, and the minimum reading that of just before sunrise. Usually, but not always!
Times when nights are very warm are usually cloudy. The clouds form a blanket that keeps us warm. Because they also block the sun in daytime, the daily maximum temperature may be almost the same as the daily minimum. The times when maxima and minima occur may become vague. As a complication, warm nights tend to happen when warm air comes to us on the wind. Then much colder air often follows. If the cold air arrives before 9 am, it will lower the minimum temperature reading, destroying the evidence of a warm night.

Thermograph Traces

I do not have a thermograph that makes a continuous temperature trace. The trace for Tamworth Airport can be seen here.(Choose a date.)

For this month’s warmest night, the Tamworth thermograph trace shows that the daily minimum temperature value is misleading due to these factors. The night was much warmer.
Between 5:30 pm on the 22nd and 5:30 am on the 23rd, the lowest temperature, which came at 7:40 pm, was 17.8°. Most of the night, from midnight to 4:00 am, was above 20°! Yet the (Tamworth) minimum for the 24 hour period was 12.5°.
Earlier in the month, in the 24 hours to 9 am on the 6th, the conventional maximum and minimum values were highly misleading. The daily maximum was the very last reading (10.0°) and the daily minimum the very first, 24 hours earlier (6.5°). The afternoon maximum temperature was 8.0° and the pre-dawn minimum temperature was 8.2°. On that date, the day was 0.2° cooler than the night!

This was the fifth wettest June in history, and had the second coldest day in this century.
Average temperatures were several degrees high until the last week, when they fell to three degrees low. In times of cloud and rain, cold days followed warm nights; at other times warm sunny days followed cold nights. There was one extremely warm night and one extremely cold day. The night before the 19th did not get cooler than 12.8°, making it the 5th warmest June night in this century. On the 27th the maximum temperature was only 8.5°: the second coldest day in this record from 1999. People remember the Friday before Queen’s Birthday in 2007 being bitterly cold, but that day reached 8.8°. The 20th of that month was the coldest, reaching only 8.3°.
This month, there were 8 frosts (usually 13) the coldest night being -1.8° in the screen.
Rain fell on 17 days, one day short of the record number here in any month (18 in June 1950!). The highest reading was 37.0 mm recorded on the 5th. As in May, the afternoon humidity was very high (seldom below 50%).

Comparing June months

The mean daily maximum temperature (16.4°) was very low, just not nearly as low as in June 2007 (14.3°). On the other hand, the mean daily minimum temperature (5.8°) was very high, as it was in June 2005, 2008, 2009, and 2013. The average temperature for the month (11.1°) was 0.8° above normal. Similarly, the subsoil temperature (16.8°) was 1.5° above normal.
The daily temperature range, normally 15.0°, was 10.6°, the narrowest yet seen in June, narrower than in 2007. Skies were rather cloudy, and the dew point normal.
The phenomenal rainfall of 114.8 mm was in the 97th percentile. There have been four wetter June months since 1883, but they were all before 1931. Thus, this is the wettest June in 86 years! Now, the greatest rainfall “shortage” is the 36-month total (1636 mm) which is in the 16th percentile. Greenhatch Creek is barely flowing, and a neighbour’s dam is almost full.

Data. Rainfall figures for this month are from the automatic rain gauge at Manilla, published on the internet by the Bureau of Meteorology as Station 55031. All other data, including subsoil at 750 mm, are from 3 Monash Street, Manilla.

Until the last week of May, the warm weather of March and April continued. Three nights (early mornings) were more than eight degrees warmer than normal. At 16.5°, the early morning of the 1st was the second warmest for May in this century after 16.9° on 3/5/2000. The first frost (a black frost) came on the 25th, not as late as in 2014, when the first frost came on the 8th of June! (More frost information is here.)

I recorded rain on 7 days (normally 3 in May) but 4 of them had less than 2 mm. The highest reading was 13.8 mm on the 2nd. The afternoon humidity was very high (seldom below 40%) which may explain the bothersome mosquitoes.

Comparing May months

The month was warm, especially at night, but not as warm as May in 2007 or 1999.
Skies were more cloudy than usual, at 45% cloudy mornings (more than 4/8 cloud). May is usually sunny, with only 24%, but both 2014 and 2015 had a record 52%
The total rainfall of 34.5 mm was near the average of 41 mm, in the 54th percentile. (Since 1998, every May rainfall except 2011 has been below average.) For the seventh month in a row, there are no serious rainfall shortages for totals for any number of months. Again, the greatest shortage is the 48-month total (2211 mm) which is now in the 14th percentile. Ponds persist in Greenhatch Creek, but a neighbour’s dam is dry.

Data. All data, including subsoil at 750 mm, are from 3 Monash Street, Manilla. Rainfall data up to 26/3/15 is from Manilla Post Office, Station 055031.

In the whole month, only one day and seven nights were cooler than normal. Days and nights warmed together. Weekly average temperature was 4.1° above normal early in the month, and again 3.5° above normal at the very end.
Rain was recorded only on the 10th (5.8 mm) and the 11th (13.0 mm). While the early morning dew point was high only when it rained, the afternoon humidity was always high, falling below 30% only once.

Comparing April months

Daily maximum, minimum, and mean temperatures were all very high but not record values for April. The mean of 20.5° was beaten by 20.6° in April 2005. In that month, this month’s daily maximum (29.0°) was also beaten (29.5°). This month’s daily minimum (12.1°) was beaten by the record value of 12.2° set in 2014.
The subsoil temperature, and other variables were near normal.
The total rainfall of 18.8 mm was well below the average of 40 mm, in the 32nd percentile. However, for the sixth month in a row, there are no serious rainfall shortages for totals for any number of months. Now, the greatest shortage is the 48-month total of 2191 mm, which is in the 12th percentile. Ponds persist in Greenhatch Creek.

Data. All data, including subsoil at 750 mm, are from 3 Monash Street, Manilla. Rainfall data up to 26/3/15 is from Manilla Post Office, Station 055031.

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Back-dated monthly reports

Monthly and seasonal weather reports for Manilla now extend back more than nine years to June 2007. [Select ARCHIVES for the month following.]
"Manilla 3-year climate trends" graphs and reports extend back to May 2010 as consecutive months. Earlier graphs and reports are accessed in ARCHIVES September 2002, 2004, 2006, and 2008.